TPA3116D2 - The amplifier hums only in one potentiometer position

I have such a small problem, I have just received a PCB amplifier based on two TPA3116 2x100w dice from China, something on the principle of dual mono. The problem is that the amplifier has a lot of noise, but only when the potentiometer is turned to half of the scale, the noise disappears. It's a bit strange literally at the beginning of the scale the noise is negligible when I get to the middle of the scale it is already significant when I get close to the max in the sweat it is minimal as at the beginning of the scale. Apart from that, the amplifier itself sounds really decent. I supply it with 20V, while the speakers have 4R impedance. Could it be the fault of the potentiometer itself? Is anything else causing these symptoms? The tile is exactly like in the photo.

If it is noise, you can assume that for some reason the amplifier is excited at high frequencies - you would have to check it with an oscilloscope.

Michael1995 wrote:

I supply it with 20V while the speakers have 4R impedance

And what should they be? Seeding and load resistance? What do you supply from? This is not an inverter by chance?

The amplifier can be supplied with voltage in the range of 12-24V. 2x100W is achieved at 2R according to the catalog note, it can easily work with 4R and 8R. Originally, the TPA3116D2 is a 2x50W amplifier, here are two such dice, but they are bridged, hence 2x100W at 2R. This is how I power it from a laptop power supply. On the diyaudio forum, most people recommend such a power supply for this board.

Maybe you get something from the signal source and you would need to connect something analog, and the second problem is the power supply in the configuration with this amplifier causes interference.

The CD player is currently used as the source. Or is it the fault of the CD output condenser? Originally there was 47uF at the output, and I put a foil but 4.7uF according to the advice of a user of an audio forum, there were no problems but maybe the amplifier is not enough for this. Could it cause such an effect?

Write which power supply you supply the amplifier with.

I have already written 20V 4.7A laptop power supply, but I doubt that this is the reason because from what I know and read, 90% of users power these boards from laptop power supplies. Besides, I tried this amplifier today on three different power supplies, including one 12V and the same effect all the time. For the sake of peace, tomorrow I will run it on the linear power supply and try to connect another CD player.

Maybe you just need to change the power supply. These 90% of users did not report any problems?

Michael1995 wrote:

It was originally there at the exit 47 uF, and I put foil ale 4.7 uF

Why?

I replaced them because electrolytes in the audio path are the greatest evil in the world Besides, with my amplifiers which have 50k input impedance, smaller output capacitors are enough.
I changed the power supply of the amplifier to linear zero difference, there is still noise only in the middle of the potentiometer scale at the beginning and end silence. I changed the sound source, still the same :(

Added after 15 [minutes]:

About me is exactly the same as in this movie.
https://youtu.be/IXgoO_mXsmo

I did not find any complaints about the noise on the web. It remains to carefully review the module for the mistake of replacing elements. How do I understand the set you bought ready assembled?

Ok, I am about to review the board for elements. And e.g. a potentiometer with a switch can cause such an effect?

Or maybe the potentiometer itself is to blame?

The blonde question: the noise is completely "white" or has a different character? Some kind of hyperexcitation?

Pure white noise is nothing else. I changed the potentiometer to another without a switch, the same thing I'm running out of ideas Everything is correct on the board :D

Added after 14 [minutes]:

See the movie on YT to which I gave the link, the noise is exactly the same so the guy had a brum, I don't have it. This is the first time I have seen something like this :D

Added after 48 [minutes]:

I just lowered the default PCB GAIN from 26dB to 20dB. Unfortunately, that didn't help either

I just bought this tile from Hi .... sz But ...
Chip miracle. The Americans did a great job.
The chinols, on the other hand, spit what they could. It just hums when there is nothing on the line. Even when I have a very low level of noise, I have the speakers on my desk. Even if I pull out the cable, it sounds the same. I have better cables. I gave another power supply - the same.

EDIT : this amplifier is set too high for me GAIN (see TPA3116 GAIN FIX on Youtube). Mine is 36dB. I desoldered the resistors R3, R4, R9, R10 and instead of R4 and R10 I gave 5.6kOhm.
First success.
The second thing according to the internet is potentiometer . Nobody understands why 50k B is there.
Everyone suggests 10k A (logarithmic).
According to the measurements with an oscilloscope, this finally eliminates hissy from the background (I just ordered one like on the board).
Second success (yet to be done).

I tried on a 12V LED power supply. GAIN alone did a lot. I will see the potentiometer.
Ultimately it wants to power from the PC. Because I have speakers next to the monitor and I want it to start together with the PC. Here you can clearly hear the background of the working machine (I think I have 6 fans). I have to filter it out somehow if I can handle it (I'm not an electronics engineer). If anyone could advise something, I would be grateful.

EDIT2 : I replaced the potentiometer with a 10kA log for PLN 5 (they were also cheaper). For me, an amateur, exchange a muck because the potentiometer has 8 pins. The exchange resulted in the lack of background noise for my needs (loudspeakers next to the monitor at a distance of 80 cm ...). I recommend
I have not mastered the power supply from the PC. I put the signal through the voltage regulator (without lowering it) hoping it would help. It didn't help. I made 5V control from PC to a single relay (module) and separate power supply from the LED power supply, which works for me all the time. No audible and nuisance noise in the absence of sound.